This invention relates generally to crop harvesting and threshing machines, more commonly known as combines, and more particularly, to the apparatus used to indicate and control the clearance between the threshing concaves and the threshing apparatus. Specifically, the invention is directed to a concave adjustment mechanism which indicates the positioning of the concaves to the operator within the operator's cab and which is adapted to permit the concaves to drop to a fully lower position upon the exertion of a predetermined amount of pressure between the threshing apparatus and the concave, such as when a foreign object, like a rock, is fed into the combine. The invention also encompasses an improved system for adjusting the clearance between the threshing apparatus and the concaves. This invention is applicable to all types of combines which utilize some type of an adjustable concave system beneath a threshing machanism, although it will be discussed primarily in the context of use within an axial flow type of combine utilizing multiple threshing and separating rotors.
Conventional combines pass the crop material to be threshed between a rotary cylinder and a stationary concave in a direction that is normal to the axis of the rotating cylinder and parallel with the longitudinal axis of the combine frame. In this system much of the grain contained in the crop material fed to the cylinder and the concave passes through the concave as threshed grain. The remainder of the material is conveyed to separating components of the combine that traditionally include reciprocating or oscillating straw walkers, grain pans and chaffer sieves. Occasionally, foreign objects, such as stones or pieces of metal, are picked up by the combine header and fed via the infeed housing into the threshing cylinder. When this occurs, some damage can be inflicted upon the generally semi-cylindrical concave which underlies the threshing cylinder by the foreign object as it makes its single pass about the cylinder. Since the threshing concave and cylinder extend transversely across the width of a conventional combine, any damage that is inflicted upon the concave or cylinder will be along a rather narrow path.
Combines of the axial flow type, in contrast, utilize single or dual rotary threshing and separating apparatus, typically rotors, that permit the crop material to pass over the concave during the threshing process three or more times. The concave generally run from front to rear and underlie a single or dual rotor system that is parallel to the longitudinal axis of the combine. An alternative design approach utilizes a rotary threshing and separating system wherein the rotor and the concaves lie transverse to the longitudinal axis of the combine. In either design, the longer area of contact between the rotors and the concave of necessity greatly increases the risk of damage to either or both the rotors and the concaves when foreign objects such as rocks or metal are fed into the threshing apparatus.
The need, therefore, to protect the concaves and the rotors from damage which can occur by the passage of foreign objects, such as rocks or metal, into the threshing apparatus is far greater in the axial flow type of combines than in the conventional type of combines. Therefore, various protective devices are used to minimize the damage that may occur to these components. Stone traps have been routinely utilized in an attempt to collect stones and other hard objects prior to their entering the threshing apparatus. These traps are generally located in the infeed housing. Shear bolt protective mechanisms are provided with the concave support frame so that when pressure above a predetermined level is exerted between the rotor and the concaves, the shear bolt fails permitting the concave to drop to a fully lowered position. This lowering of the concaves thus prevents the foreign object from being forced by the rotating rotors against the concaves and inflicting damage upon either mechanism.
The dropping of the concaves due to the failure of a shear safety mechanism, however, presents another problem which has not been previously addressed in axial flow type of combines. Since the dropping of the concaves upon contact with a foreign object between the rotor and the concave occurs without any operator involvement, it is entirely possible for an operator to continue harvesting crop material from the field after the shear safety mechanism has failed without being aware of the fact that the concaves have dropped. This dropping of the concaves in almost all cases will expand the clearance betweeen the rotor and the concaves beyond the optimal threshing distance. It is possible for an operator harvesting small grained crop material, such as wheat, to have a 10% to 15% drop in efficiency of the machine when the concaves have dropped to the fully lowered position. It is even possible for the operator to continue working all day without knowing the concaves have dropped since there is no indicator within the cab which readily transmits this information.
The foregoing problems are solved with the design of the machine comprising the present invention by providing a concave adjustment indicator coupled with a concave shear bolt failure mechanism to indicate to the operator when the shear safety mechanism has failed and the concaves have dropped to the fully lowered position.